The present invention relates to an amplifier circuit, comprising a main current stream of a controllable semiconductor device having a control input, a control means having a control output coupled to the control input for controlling the main current stream, and a compensation circuit having a compensation output coupled to the control input for compensating the controllable semiconductor device.
The present invention further relates to an integrated circuit, a transmitter and a wireless telephone provided with such an amplifier circuit.
Such an amplifier circuit is known from U.S. Pat. No. 4,481,481. The known amplifier circuit comprises a controllable semiconductor device in the form of a common emitter transistor having a control input formed as a base, a control means in the form of an emitter follower transistor having a signal input and having a control output as its emitter, and a compensation circuit in the form of a current mirror having an input connected to the collector of the emitter follower transistor, and having a transistor whose collector is the compensation output which is connected to the base of the common emitter transistor. The amplifier circuit also comprises a DC-current source connected to a terminal of the power supply and to the collector of the emitter follower transistor. A part of the current provided by the current source flows to the collector of the emitter follower transistor and the other part flows through the current mirror. Any rise or fall of an input signal on the signal input of the emitter follower transistor will pull up and pull down, respectively, the base of the common emitter transistor, which functions as a driving stage or end stage, whose available drive is thus maximized. Independently of the state of conduction of the emitter follower transistor, a DC-current will flow at least through the current mirror of the compensation circuit. This causes the compensation circuit in the known amplifier circuit to be permanently active, and which has the drawback of that it exists of a negative effect on the consumption of DC-current from the power supply.